Field of the Invention
This invention relates to separators and, more particularly, to novel systems and methods for optimizing performance of liquid-liquid separators.
Background Art
Water purification is an activity required to meet various requirements. For example, waste water from industrial processes may require remediation before returning the basic water stream into a riparian flow, estuary, lake, sea, or other supply. Similarly, production water generated during production of petroleum, natural gas, or other petroleous materials may require remediation before disposal in any one of several ways.
For example, oil needs to be removed from water before it is re-injected into a disposal well. Otherwise, fouling will reduce the life of the disposal well. Similarly, if industrial contaminants or production water is re-injected into a disposal well, potential ground water contamination may be a consideration requiring removal of certain species of contaminants in the water.
On the other hand, production water may contain valuable oil that should be separated from the water for inclusion in the production of a well. Accordingly, water may be purified in order to separate out available petroleous product. By the same token, water separation from oil to a volume fraction of less than one percent or a mass fraction of less then one percent may be required to obtain optimum prices for crude oil.
Technologies have been developed for separating species of liquids or disparate phases (where each species is considered to be a separate phase, even within the same liquid state). U.S. Pat. No. 6,607,473, incorporated by reference herein; discloses certain embodiments of liquid-liquid separators.
As a practical matter, separation processes, specifically liquid-liquid separation processes, are a staple of chemical engineering practice. As a direct result, certain rules, formula, procedures, rules of thumb, and the like may typically be relied upon. Nevertheless, much of settling theory originates in static settling tanks or settling ponds. These are not actually static, but the pond or tank wall itself is static. The flow passes through as the effects of gravity on the differentials of buoyancy between constituents within the flow thereby separate them out, coalesce, or otherwise render them separable from one another.
In the chemical engineering arts, much of settling theory applied to stationary tanks has also been applied to the extent deemed appropriate to rotating separators, such as cylindrical tanks. Cylindrical tanks may have a fixed wall with a moving rotor inside. Other cylindrical tanks may actually rotate in their entirety.
However, prior art systems suffer from non-optimized operation. The controlling parameters to design them and scale them rely on conventional settling theory. The controlling parameters recognized are built into the very designs. They lack control variables effective to control and adjust operations with changing conditions “on the fly” during operation. They lack control systems and control mechanisms by which to control outputs by manipulation of control variables.
It is the conventional wisdom in settling systems to maximize the settling area of a settling tank. This means that the interface between the two principal species (phases) being separated from one another should have a maximum area. When one thinks of diffusion across a boundary, increased area in the diffusion equation suggests a higher total amount of diffused species. In other words, the total flux is increased when the rate of flux per unit area is multiplied by a larger, even the largest, available area. Thus, it is conventional wisdom that the surface area of the interface between the separating phases be maximized.
If a parameter changes, such as rotational velocity, pump throughput, constituents of the influent, fractions of influents, or the like, the interface radius between the separating phases simply finds its own new equilibrium position. There was no control of that interface. The control of the output of the separated phases was a result of the design parameters, and not manipulated by the operational parameters of the machine. It could be affected by the influents and by the temperature of the influent (which could be uncontrolled as a result of the environment, or could be controlled by adding heaters into the system), but the design was the design.
The '473 patent provided development of a mechanism to alter the set point of operation of a rotating separator. That mechanism was a recognition that the back pressure on the comparatively lighter phase being separated could modify the position (radius) of the surface of revolution, actually a the thin region of revolution, that constitutes the interface between the separating phases. Thus, an operator could specify the radius (radius of revolution of the dispersion band or interface) and maintain that position by altering the back pressure on the output or effluent line of the lighter phase.
That is, the understanding that back pressure could affect the radius of the dispersion band was developed in U.S. Pat. No. 6,607,473. However, the ability to determine what that radius should be (other than a “maximum area”) has never been established to Applicants' knowledge in the prior art.
Moreover, no principal or mechanism has been developed for understanding the relationship between input variables (e.g., independent variables, properties, and the like of the incoming influent and the geometry of the separation device) as they may affect the desirable radius required of a dispersion band. Moreover, the relationship between the position of the dispersion band and the output properties has not been established, nor even the influence of the incoming input parameters thereon. Moreover, no mechanism for establishing control therebetween has been found in the prior art.
What are needed are mechanisms, operating principles, and even an understanding of the underlying phenomena and their parameters that may affect the material properties or behaviors of processed streams. Moreover, what is needed is a mechanism for understanding the effect of changes of those parameters. What would also advance the art are a system and apparatus as well as an operational method, even an experimental determination method, for determining and controlling the parameters on which the actual output depends.
For example, it is conventional wisdom, as discussed above, to maximize the area of the surface of rotation of the dispersion band in a rotating separator. However, experiments by Applicants demonstrate that this has a negative effect on the actual turbidity or purity of the output species. At present, it would be an advance in the art to find a principle and a mechanism whereby a previously selected quality of the output may be controlled by controlling any operational parameters within a separator after the time of design and construction. For example, it would be an advance in the art to provide any type of online quality control of the output by adjusting an operational parameter. This should be based on an understanding or measurement of the inputs, operational set points, or both.
It would also be an advance in the art to provide a principle and mechanism for determining an optimal location for the radius of the dispersion band (phase interface) within a separator. It would be a further advance in the art to provide a method and apparatus for optimizing any output parameter, such as purity, volumetric flow rate, efficiency, preferential purity of one species, or the like based on modifying internal parameters, and more particularly on the fly during operation.